Why won't my Activity start?

Why won't my Activity start? - android

I have an industrial app which is remotely controlled from a PC. The app has 2 slightly different versions - one for a Honeycomb tablet and the other for a Gingerbread phone. The differences are to take advantage of unique features in the hardware (e.g., the phone has a better camera, the tablet can display bigger graphics) but the Activity-starting code is the same.
A thread in the app receives commands from the PC and displays different screens (i.e., starts different Activities). It works fine on the phone but on the tablet one activity won't start, but throws no exceptions. Breakpoints and logging in that activity's onResume() are never hit, even though they are on the phone. Here's how I try to start the activity . . .
try {
Intent svc = new Intent(ctx, RemoteControlActivity.class);
ctx.startActivity(svc);
}
catch (Exception e) { // or ActivityNotFoundException e
Log.d("ShowButtons(normal)", "startActivity failed");
}
(ctx is a Context - in the debugger the Context is the same for both the working on non-working cases)
The activity which is failing to start on the tablet is defined like this in the manifest . . .
<activity
android:launchMode="singleTask"
android:label="#string/app_name"
android:windowNoTitle="false"
android:configChanges="orientation"
android:screenOrientation="landscape"
android:name="RemoteControlActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
This is driving me batty - thanks in advance for any help!

Try this
Intent svc = new Intent(ctx, RemoteControlActivity.class);
svc.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
ctx.startActivity(svc);
According to the docs
When using this flag, if a task is already running for the activity you are now starting, then a new activity will not be started; instead, the current task will simply be brought to the front of the screen with the state it was last in

I found a solution. I'm posting it this way so I can mark it as "answered" incase anyone else runs into this and is searching for a workaround. But I admit I don't understand why it works.
The breakthrough was discovering that it mattered what activity was currently on the screen when I was trying to start RemoteControlActivity. The failure was happening when I had an activity that displayed some graphics on the screen. I substituted a different activity that displayed some buttons and the problem went away.
Looking at the Manifest I noticed that the "good" activity was set to:
Android:launchMode="singleTask"
and the "bad" one was set to:
Android:launchMode="singleInstance"
When I changed the graphics activity to "singleTask" the problem went away.

Related

Lollipop: making my activity stay in the task that launched the share intent

“My First App” has an activity that handles a “share” intent. Its activity in AndroidManifest.xml looks like this:
<activity
android:name="com.example.foo.myfirstapp.MainActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.SEND"/>
<category android:name="android.intent.category.DEFAULT"/>
<data android:mimeType="image/jpeg"/>
</intent-filter>
</activity>
In KitKat, sharing an image from the album to “My First App” causes MainActivity to be part of the album’s task. This is the desired behavior.
In Lollipop, sharing an image from the album to “My First App” causes a new instance of “My First App” to be launched. If I look at the overview screen, the album task is there...and then there's a separate entry for "My First App". If I share another image, I wind up with two instances of "My First App"...etc.
Question: How do I make Lollipop process the share intent in the same way as KitKat?
Here's what I've done:
I notice that the intents sent from the Album have different flags set depending on the OS. (I got these using getIntent() and looking at mFlags.)
Kitkat: 0x80001 (524289): FLAG_GRANT_READ_URI_PERMISSION, FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET
Lollipop: 0x18080001 (403177473): FLAG_GRANT_READ_URI_PERMISSION, FLAG_ACTIVITY_MULTIPLE_TASK, FLAG_ACTIVITY_NEW_DOCUMENT, FLAG_ACTIVITY_NEW_TASK
From reading http://developer.android.com/reference/android/content/Intent.html, it seems that these last three flags are causing the problem. Specifically
When paired with FLAG_ACTIVITY_MULTIPLE_TASK both of these behaviors (FLAG_ACTIVITY_NEW_DOCUMENT or FLAG_ACTIVITY_NEW_TASK) are modified to skip the search for a matching task and unconditionally start a new task.
I’ve been attempting to “override” these flags by specifying android:launchMode and android:documentLaunchMode in the activity in AndroidManifest.xml without success.
From http://developer.android.com/reference/android/R.attr.html#documentLaunchMode, using documentLaunchMode “never” seems promising, since
This activity will not be launched into a new document even if the Intent contains Intent.FLAG_ACTIVITY_NEW_DOCUMENT. This gives the activity writer ultimate control over how their activity is used.
but this didn't work.
I also considered android:taskAffinity, but there doesn’t seem to be a way to say “please prefer whatever task launched you”.

Afraid you can't do anything about this. It isn't under your control. This is a change in the way the "Album" app is launching its "share" Intent. If it doesn't want your Activity in its task, you can't force it in there.
If you have issues with having multiple instances of your "share" activity, you could declare your "share" activity as launchMode="singleTask" or launchMode="singleInstance" (depending on your needs. This may, however, break other things.

android:alwaysRetainTaskState = false not being respected, task state always retained

I would like my app to exhibit the default behaviour described for android:alwaysRetainTaskState in the Android documentation:
Normally, the system clears a task (removes all activities from the
stack above the root activity) in certain situations when the user
re-selects that task from the home screen. Typically, this is done if
the user hasn't visited the task for a certain amount of time, such as
30 minutes.
This isn't what I'm seeing. Even after >1 day, re-starting my app using the launcher icon returns the user to the place where they left it.
For example, after a fresh install my app displays a home screen activity H when launched. The user then navigates to detail activities: H -> J. On relaunching after a long time, I would like the user to see H, but instead they see J.
These are the flags set on my activity in the AndroidManifest.xml:
<activity
android:name=".AppHomeScreen"
android:label="#string/app_name"
android:alwaysRetainTaskState="false"
android:launchMode="singleTop"
android:windowSoftInputMode="stateUnchanged">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
I am running Android KitKat 4.4.2.
Is there any reason why I might not be seeing the expected behaviour here? I know that I could set android:clearTaskOnLaunch or android:finishOnTaskLaunch to clear the task every time the user leaves the app, but this is too aggressive, I'd like the described behaviour where the state is only forgotten after a long period of inactivity.
(The Android documentation doesn't seem to guarantee the behaviour, only that the task is cleared in "certain situations" and "after a certain amount of time, such 30 minutes". Maybe the default behaviour was changed and the Android docs are out of date?)

This behaviour is manufacturer/vendor-specific. On different devices you will see different behaviour. There are devices that aggressively clear out tasks and others that retain task state for much longer periods of time.

Fail to resume the activity stack during 1st launching after installation

Our application has a splash activity (main activity for launcher) and many other activities. In most cases, when the user switches the application into background and resumes it from launcher, the old activity stack is resumed and top activity in that stack is shown as expected.
However, when the apk is just installed on the phone, or a new apk (with higher version) of the same application is installed, its behavior is strange. When the application is switched to background and resumed from launcher, the previous activity stack is not resumed and the splash activity is always shown. If we resume the application from recent applications list, the activity stack is resumed as expected. Only after killing the task from recent applications list, everything becomes normal again. The previous activity stack will always be resumed correctly until it is replaced by another apk installation again.
My Android version is 4.1.2 and I am using its default launcher.
Following is configuration of the splash activity.
<activity android:name=".welcome.activity.SplashActivity" android:screenOrientation="portrait">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
Who has any idea about the strange behavior? Thanks in advance!

Finally I have found this is an issue of Android system. It has already been discussed in Activity history stack wrong upon first install on device?.
I have adopted a workaround stated in https://code.google.com/p/android/issues/detail?id=2373#c40 and it works well, i.e. adding the following code in SplashActivity.onCreate():
if (!isTaskRoot()) {
Intent intent = getIntent();
String action = intent.getAction();
if (intent.hasCategory(Intent.CATEGORY_LAUNCHER) && action != null && action.equals(Intent.ACTION_MAIN)) {
finish();
return;
}
}

I'm not really able to tell what's going on without knowing more about your app. I would look into:
The launchMode manifest element: android:launchMode
Check your activities are not being destroyed and recreated by the system: Recreating an Activity
If you are doing anything with fragments and if these are maintaining state correctly
Sorry, bit of a guess!

Since you only want to show your Splash Activity once, you can use finish() after you launched the Main Activity, that should solve your problem.

App completely restarting when launched by icon press in launcher

I'm in the process of trying to make a release build of my first android app to send to a few testers. However, I ran into a problem with it. When you exit the app and then re-enter it by launching it via its icon, it restarts the whole app instead of returning to it's previous location. This occurs even if you re-enter right after exiting. However, it does not happen if I hold the Home button and launch it through the recent apps list.
I've searched online for others having this problem and there are a few, but no one has ever had a solid answer as to why it's happening to them. It's been suggested in old questions to set the launchmode to singletask or singleinstance in the manifest file, but that hasn't helped me, and besides - from what I understand, the default behavior for android is to return to the previous state of the task in this situation, so I don't know why I would need special manifest options to make it do that.
The most bizarre thing about this problem is that if I use eclipse and the debugger to put the app on my phone, this problem does not occur. I don't even need to be connected to the debugger, it seems like as long as I have a debug version of the app, the problem doesn't occur. But if I use a release version (I create it using the Android Tools - Export Signed Application Package menu option in Eclipse), the problem happens.
If anyone has any insight as to what is causing this, I'd love to hear your thoughts.

I had the same problem with an application and I resolved this behavior adding flag "android:launchMode="singleTop"" instead of "android:launchMode="singleTask"" in the <activity> declaration of your AndroidManifest.xml file. Hope this will help somebody.

So far I've found out that it's an issue based on how you install it in your real device, specifically:
If you simply copy and paste the APK to your device's local storage and install it from the device, regardless of whether it's signed or unsigned or taken from bin folder, it shows this behavior, app restarts from menu icon.
If you install it using one of the following options, This issue does not appear:
Go to sdk/tools/ using a terminal or command prompt then type
adb install <FILE PATH OF .APK FILE>
In Linux, type:
./adb install <FILE PATH OF .APK FILE>
Simply run your project from Eclipse.
I would be pleased to know if there's any possible way to distribute correct APKs for beta testing. I already tried exporting a signed APK because when you copy and paste an APK and install it manually it shows the rogue behavior.
Update:
I found out a solution. Follow these two Steps:
Set android:launchMode="singleTask" = true for all activities of your app in the AndroidMainifest.xml inside the activity tag.
Put this code in your Launcher Activity's onCreate().
if (!isTaskRoot())
{
final Intent intent = getIntent();
final String intentAction = intent.getAction();
if (intent.hasCategory(Intent.CATEGORY_LAUNCHER) && intentAction != null && intentAction.equals(Intent.ACTION_MAIN)) {
finish();
return;
}
}
This behavior is a bug in Android. Not a special case.

// To prevent launching another instance of app on clicking app icon
if (!isTaskRoot()
&& getIntent().hasCategory(Intent.CATEGORY_LAUNCHER)
&& getIntent().getAction() != null
&& getIntent().getAction().equals(Intent.ACTION_MAIN)) {
finish();
return;
}
write the above code in your launcher activity before calling setContentView. This will solve the problem

You could use launchMode as singleTop to the Launcher Activity in AndroidManifest.xml
<activity
android:name="<YOUR_ACTIVITY>"
android:label="#string/app_name"
android:launchMode="singleTop">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

It is the default behavior in Android. For the debug builds it works differently for some reason. It can be solved by adding android:launchMode="singleInstance" to the activity, you want to restart after you launch from the icon.

Add this to your first activity:
if (!isTaskRoot()) {
finish();
return;
}
super.onCreate(savedInstanceState);

Try using android:alwaysRetainTaskState as shown in the following example:
<activity
android:name="com.jsnider.timelineplanner.MainActivity"
android:alwaysRetainTaskState="true"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

For me, I found that I had erroneously posted NoHistory = true in my activity attribute
[Activity(NoHistory = true, ScreenOrientation = ScreenOrientation.Landscape)]
This prevented the app resuming into this activity and restarted

You can try to set android:alwaysRetainTaskState="true" for your launcher activity in AndroidManifest.xml.
<activity
android:name=".YourMainActivity"
android:alwaysRetainTaskState="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
For details you can see https://developer.android.com/guide/topics/manifest/activity-element.html#always

I see this issue on Android TV in 2019. Is there a better fix for it? other than
if (!isTaskRoot()) {
finish();
}
It works but looks like a hack more than the actual solution.

All of the solutions above didn't work consistently on all of my devices. It worked on some Samsung but not all.
The cause of the problem for me was installing the APK manually.

For me the fix was adding LaunchMode = LaunchMode.SingleTop to my Activity attribute over the Main Activity:
/// <summary>
/// The main activity of the application.
/// </summary>
[Activity(Label = "SilhuettePhone",
Icon = "#drawable/icon",
Theme = "#style/MainTheme",
MainLauncher = true,
ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation,
ScreenOrientation = ScreenOrientation.Portrait,
LaunchMode = LaunchMode.SingleTop,
WindowSoftInputMode = SoftInput.AdjustResize)]

I had a problem with a restarting app, my problem was in themes:
I have differents fragments and I would have one background for all. But this cause a restarting app in some devices(.
I've deleted this line in themes and this helped:
item name ="android:windowBackground">#drawable/background /item

Removing task affinity rather than launch mode has worked somewhat for as it has its own demerits

When you press the back button in Android, the onDestroy method is invoked (as opposed to pressing the home button, where only the onPause() method is invoked).
If you need your app to continue where it left off, save the state of the app in your onDestroy() method and load that state in the onCreate() method.

Android error, failed to set top app changed

Can somebody please throw some light on the arcane error "Failed to
set top app changed", by the activity manager?
I'm wondering what causes this error. In one of my application I'm
making a view fullscreen and then switching back. For the first time
things are ok but then if i try to make the view full screen again, I
get a crash and the error mentioned above is found on logcat.
Any help is greatly appreciated.
Reagrds,
M

I just encountered this problem today myself.. let me tell you what did the trick for me... maybe it will help you too.
anyway in my case it crashed because i overrided onActivityResult and inside that event i tried to do this:
Bundle extra = data.getExtras();
String albumId = extra.getString("id");
this is old code that got left in the application.. after deleting this everything worked as expected.
hope this helps in some way.

I had the same problem with my app, the activity crashed and "activity manager: fail to set top app changed!" in logs. Turned out to be one line of code in the onPause caused the problem. Check your onPause method of the Activity that launches the new Activity to see if something should not be done there. I think there could be many reasons causing this problem, but the basic idea is that the launching activity does something wrong when the new Activity is going to show up.

My problem was that i change orientation on activity start and needed to add android:configChanges="orientation" , like this:
<application
android:icon="#drawable/icon"
android:label="#string/app_name" >
<activity
android:name=".RiskniMilionActivity"
android:label="#string/app_name"
android:configChanges="orientation">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

Develop Reference

The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.